1. Field of the Invention
This invention is in the field of devices for holding a segment of a thin strip of material on which has been formed, or to which has been attached, a flexible beam lead and to which lead an integrated circuit (IC) chip is bonded. The fixture, or holder, is dimensioned to hold one segment of a film strip. Once a segment is attached to, or held by, the fixture, the fixture protects the IC chip and its lead frame from being damaged during subsequent manufacturing steps but permits the IC chip and a portion of its lead frame to be removed from the segment while the segment is held by the fixture. To optimize the fixture for automating the mounting of a segment on a reusable fixture and for subsequently removing the segment from the fixture, the fixture is provided with a plurality of pairs of attachment projections having wedge shaped protrusions which protrusions overlie the attachment webs of a segment. The attachment webs are located between the sprocket holes of the segment and adjacent edges of a segment. In addition, the fixture is provided with detachment openings which provide access to the attachment webs to facilitate automating the removal of a segment from the fixture.
2. Description of the Prior Art
The application listed under the heading Cross Reference to Related Applications is believed to be the most relevant prior art. FIGS. 7, 8, 9 and 10 of that application disclose a reusable fixture for a segment of a film strip that retains a segment by the use of projections or lugs which fit within the attachment sprocket holes of a segment. Use of lugs or projections which frictionally engage the handling or attachment sprocket holes has revealed two problems. One is that occassionally that portion of a segment that projects beyond a line joining the outer edges of the handling sprocket holes bends, or curls, enough so that an edge of a segment projects above the surface of the fixture. As a result the segment and its IC are not properly protected by the fixture. A second problem arising from the use of four lugs, or projections, that fit within the four attachment sprocket holes of a segment is that such an arrangement does not lend itself to automating the removal of a segment from such a fixture. Normally a segment is removed from its fixture after the IC chip and part of its lead frame has been removed. The reason this second problem occurs is that the prior art arrangements require more than the theoretical minimum forces to remove a segment from its fixture, which removal forces is substantially more than force needed to mount a segment on a fixture. The reason for this discrepancy is that if an essentially point source of force is applied to the bottom surface of a segment to remove it from such a fixture, the point of application of the force under the prior art fixture cannot be at the center of the attachment sprocket holes the centroid of the edges of the attachment sprocket holes. As a result, one side of each attachment sprocket hole tends to bind against its attachment lug which significantly increases the forces necessary to remove a segment from a fixture in which it is mounted and increases the risk of damage to the chip mounted on the segment if such is the case, and to the fixture.